XSS sanitize text panels

[jschill]

Feat:

• Adds XSS sanitization to text panels
• Add possibility to disable the sanitization via custom.ini

Questions:

• Is disable_sanitize_input a good name of the config key? And should it be in the panel section?
• Did I do the config key flow correct? (First time in go)
• Do we need to add the sanitization anywhere else? This is only targeting the text panels.

Fixes #4117